The present invention generally relates to the treatment of thrombotic conditions and more specifically to devices and methods for salvaging or recovering blood to reduce net blood loss during procedures and as a result improve the safety of these procedures for health care workers and patients.
Some of the current medical treatments of thrombotic conditions such as arterial emboli and thrombosis, deep vein thrombosis and pulmonary thromboembolic disease often require the aspiration of clot fragments following their mechanical fragmentation with one of several devices. In the process of removing these clot fragments, moderate to large amounts of blood can be aspirated along with the clot fragments. Obviously, keeping blood loss to minimum is important in any surgical procedure but it is particularly important in this setting because of the frequently associated concurrent illnesses. In addition, blood loss could be a factor limiting the success of the procedure unless the blood can be returned to the patient in someway.
Turmel-Rodrigues, et al. advocated filtering aspirated blood through a gauze sponge with reinjection of the blood with no adverse sequelae. (Manual thromboaspiration and dilation of thrombosed dialysis access: mid-term results of a simple concept. JVIR 1997, 8:813-824). During this procedure, the blood containing clot fragments are withdrawn from the thrombus area with a 50 mL syringe. Then, the removed blood is squirted through a gauze sponge into a cup, aspirated back into a syringe, and reinjected into the patient. Although this blood filtration process reduces blood loss, it has many drawbacks. First, a substantial amount of blood is absorbed into the sponge. Second, the additional filtration steps prolong the overall thromboaspiration procedure time. Thirdly, the prolonged procedure time creates a risk of overexposure to x-ray to the operators whose hands are working close to fluoroscopy. Id. Finally, the filtration procedure involves handling the blood, which creates additional risk of infection for the patient and contamination for the health care worker.
At present, there are many complex devices available for use in major surgical procedures, trauma and other settings of uncontrolled blood loss. None of these are suitable for salvaging blood during thromboaspiration procedures. For example, the apparatus disclosed in U.S. Pat. No. 5,858,238 to McRea et al. is designed for salvaging blood from a patient and selective removing water, fluids, and low molecular weight solutes in the blood. The apparatus has several connecting parts that perform these functions in a complicated blood treatment process.
Other devices relating to the removal of blood clot fragments from the blood stream include those for use in intravascular treatments, especially in patients with deep vein thrombosis conditions. These devices include filters or valves that can be implanted inside a patient to filter particulate matter from a fluid flow or to regulate the fluid flow. For example, U.S. Pat. No. 5,800,457 to Gelbfish discloses an intravascularly deployable filtration device in a conical shape. This particular device has an access port which functions as a coupling element with a distal end of an elongated debris removal instrument. The design of this device allows for the blood clot particles to be trapped on the passive filter system. The clot particles can be removed by the debris removal instrument without having to remove the filtration device itself. Additionally, U.S. Pat. No. 5,925,063 to Khosravi describes an apparatus deployable within a body vessel or organ that can function as a filter or a valve. This apparatus has a plurality of flaps comprising a fluid permeable mesh that can be configured to project toward one another and overlap each other to form a filter. The plurality of flaps can also comprise a resilient material capable of defecting and form a valve that opens when a pressure differential across the flaps exceeds a predetermined valve.
Although the aforementioned devices can be used for blood filtration, they are indicated for a long-term intravascular treatment, which requires implantation and removal of the device during surgical procedures. These devices do not satisfy the need for extracorporeal blood treatment associated with thromboaspiration procedures.
A need has remained for devices and methods for filtering blood clot particles from blood, salvaging the filtered blood, and quickly returning the filtered blood to the patient.
A need has also remained for blood filter devices that are disposable, inexpensive and easy to operate.
Briefly describing one aspect of the invention, a device for filtering blood clot particles from blood is provided. The device includes a housing having a first end defining a fluid port and an opposite end defining a suction port. The fluid port is engagable to the side arm of a catheter that is used to withdraw blood from a patient. The housing further defines a reservoir in fluid communication with the fluid port. A valve member is disposed between the fluid port and the reservoir. The valve member has a semipermeable membrane portion permeable to blood and impermeable to blood clot particles. The valve member is further provided with a one way valve portion having an open position permitting passage of fluid and particles from the fluid port to the reservoir and a closed position blocking passage of particles between the reservoir and the fluid port.
In one specific embodiment, the device has a valve member that includes at least one leaflet composed of a resilient material capable of: deflecting to achieve the open position upon receiving suction pressure from the suction port and returning to the closed position when suction is removed.
In another specific embodiment, the valve member includes a plurality of valvate leaflets, each composed of a resilient material capable of deflecting to the open position and returning to the closed position.
In yet another aspect, the housing comprises a first housing portion and a second housing portion. The first housing portion includes the first end defining a fluid port and an opposite end defining a first opening. The first housing portion further defines a chamber in fluid communication with the fluid port and the first opening. The second housing portion has a first end defining the suction port and an opposite end defining a second opening. The second housing portion further defines the reservoir, which is in fluid communication with the suction port and the second opening. The opposite end of the second housing portion is hermetically sealingly engagable to the opposite end of the first housing portion.
In preferred embodiments, a first engagement member is disposed on the opposite end of the first housing portion and a second engagement member is disposed on the opposite end of the second housing portion. The first engagement member is matable with the second engagement member to releasably secure the housing portions together. In one embodiment, the engagement members are screw threads.
In yet another aspect, the engagement member is a hinge hingedly connecting the first housing portion to the second housing portion and a lock member releasingly engaging the first housing portion to the second housing portion.
The invention further provides methods for filtering blood clot particles from blood of a patient undergoing treatment for a thrombotic condition. The methods include: providing a catheter having a side arm port for suction and introducing the catheter into a blood vessel, engaging the fluid port of a device of this invention to the side arm port of the catheter, applying suction pressure to the suction port of the device to open the valve and draw blood containing blood clot particles through the catheter, past the valve and into the reservoir, and then removing the suction pressure to close the valve and trap particles in the reservoir.
In yet another embodiment, the methods include the step of reinjecting the blood from the reservoir into the patient through the catheter. The invention contemplates repeating the steps until the blood clot particles are removed. The methods also include disengaging the first housing portion from the second housing portion, removing blood clot particles from the valve, and then re-engaging the first housing portion to the second housing portion.
Accordingly, it is one object of the invention to provide devices and methods for safely salvaging blood to reduce net blood loss during treatment for thrombotic disorders. This and other objects, advantages and features are accomplished according to the devices and methods of the present invention.